Superior oxygen transfer ability of Pd/MnOx-CeO2 for enhanced low temperature CO oxidation activity

The low temperature CO oxidation activity of Pd doped MnOx-CeO2 (MC) solid solution catalyst is evaluated to determine the role of Pd speciation and oxygen transfer. Dynamic reduction behavior of Pd2+ species in the presence of CO at low temperatures is characterized by in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) and X-ray absorption spectroscopy (XAS). H-2 temperature-programmed reduction (TPR) and CO/O-2 transient pulse experiments are conducted to evaluate the lattice oxygen reducibility of Pd/CeO2 and Pd/MC. Our results show that highly dispersed PdO species form on the freshly calcined CeO2 and MC supports. Despite the fact that similar Pd species form on the CeO2 and MC supports, PdO can be reduced immediately on CeO2 in the presence of CO, while the MC support can preserve the oxidized Pd species during CO reduction. In the case of CO oxidation, Pd2+ species are maintained through lattice oxygen transfer facilitated by the MC support. CO/O-2 transient pulse experiments confirm the higher reducibility of the MC support, which can favor CO oxidation at 50 degrees C. (C) 2017 Elsevier B.V. All rights reserved.